[Acute renal failure - how and when to treat?]

Acute renal failure is a common condition in intensive care units. The negative impact of acute renal failure on mortality has been demonstrated in recent studies. All critically ill patients should be regarded as a high risk population for renal failure. The optimization of intravasal fluid status and mean arterial pressure are preventive strategies in these patients. The use of nephrotoxic drugs (including radiocontrast media) should be avoided if possible. In cases of established acute renal failure today therapeutic strategies are still limited to best supportive care. The use of diuretics can facilitate fluid balance, however they seem to have an adverse effect on excretional renal function. A number of patients with acute renal failure need extracorporal renal support. Overload of potassium or fluids, severe acidosis, uremic pericarditis or uremic encephalopathy are urgent indications for the start of renal replacement therapy. Small randomized trials give some evidence that an early start of renal replacement therapy may be beneficial in critically ill patients. In this patient group renal replacement therapy should be considered when serum urea concentrations exceed 100mg/dl and/or when early signs of indications mentioned above are present. Large randomized multicenter trials have shown that a favourable effect on mortality can only be achieved when renal replacement therapy is supplied with a sufficient dose. Daily hemodialysis or continuous hemofiltration with a filtrate volume of 35ml/kg/h is regarded as a standard of care. There is still controversy whether continuous hemofiltration is superior to intermittent hemodialysis. Large meta-analyses could not show a difference in mortality with either one of the two therapy options.